A person who moves so slowly that it compromises the sanity of all those around him/her, leading to chaos and destruction.
"Why are you such a bleeding, dirty mess?"
"There was a slowling who held up traffic at the end of Route 3. It took him an hour and a half just to merge onto 128. The other drivers got so infuriated that they rioted, and my car got overturned. I had to crawl the rest of the way to work."
— Boys, quickly come here, a slowl is sitting on a tree! Wait, don't need to rush, he's slow